Relax and give yourself permission to have fun on a bike. Accept that ANYTHING might happen when you roll out the driveway - you might feel great, you might suck, you might have an epic ride, or it might be 5 miles. This day, your accomplishment is buckling up the helmet and going for it.
Sometimes it's easy to psyche yourself out of riding "today" because today isn't perfect enough, you're not going to set a PR, you only have time for the ride you can do, not the one you want to do (my bugaboo - used to be that if it wasn't 6 hours, it wasn't a ride, so I spent a miserable several months without much riding until I got THAT notion out of my system).